A loader work vehicle has a front loader attached to the front of a tractor. The front loader has mounting frames provided at right and left sides of a tractor body, booms vertically swingably connected to upper portions of the mounting frames, a working implement such as a bucket swingably connected to distal ends of the booms, boom cylinders for swinging the booms, and an implement cylinder for swinging the working implement. Each of the right and left mounting frames has a support base protrude laterally outward of the tractor body, a main frame attached to a laterally outward end of the support base to project upward, and a side frame detachably attached to the main frame to project upward. Each boom has a proximal end thereof vertically swingably attached to an upper end of the side frame.
The conventional loader working vehicle of this type includes a control valve disposed outside or in an upper position of the main frames of the mounting frame for controlling the hydraulic cylinders of the front loader (JP2001-140276A, JP10-280473A, JP10-280464A and JP7-207701A).